ASPHALT WALKS - SIDEWALKS.Asphalt is used for sidewalks both in the form of a monolithic sheet and in blocks or tiles, in much the same way as for carriage-way pavements, except that the foundation need not be so strong nor the wearing coat so thick.
The material for the wearing coat of artificial sheet asphalt foot-way pavements may be mixed softer than for carriage-way pavements, as the former are not required to bear the heavy loads of the latter. The softer the mixture the greater its life, since the greater the amount of oil the longer the time before the pavement will be rendered brittle by the effect of volatilization and oxidation. Asphalt is unsuitable for unfre quented walks, since cracks due to expansion and contraction are not re-cemented by the pressure of traffic (§ 654). Monolithic asphalt foot-way pavements are not common in this country, the only city in which they are used to any considerable extent being Washington, D. C., where the material removed from old asphalt carriage-way pavements in making repairs and in re-surfacing is used for foot-ways. Such pavements with a 3-inch hydraulic-cement concrete base and a 1-inch wearing coat usually cost, exclusive of grading, from 90 cents to $1.00 per square yard.
Sheet asphalt foot-way pavements are used to a considerable extent in European cities, particularly in Paris. They are made of asphalt mastic or, in French, asphalte coule, which consists of an as phaltic limestone to which has been added some asphalt, usually that from Trinidad. The material is heated and carried to the walk in buckets, and being of a consistency to flow slowly is poured out upon the foundation and spread to the desired thickness, usually about f of an inch, and smoothed with wooden floats. Some coarse sand is usually rubbed into the surface to keep it from being slippery. When cool the pavement is ready for use.
Asphalt sidewalk-paving tiles are made 2 1/2 inches thick having a top surface 8 inches square or a hexagon of the same area. For a description of the composition of the blocks and of the method of making them, see Art. 4, Chapter XIII, page 447. The blocks, or tiles as they are commonly called, are laid substantially as described for asphalt block carriage way pavements—see § 682-91.